JPH10254282A - Fusion by single pass for sheet feeding type multilayer both-sided copying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform excellent fusion without performing an intermediate fusion in a multilayer both-side copying method, by making respective outside diameter of first and second roller equal, and respective thickness of elastic coating material thereon equal. SOLUTION: A fusing station 25 includes a pair of rollers 1 and 11. The respective roller 1 and 11 include rotary body 3 and 13. The respective heat conductive bodys on both side are substantially provided with the same diameter, and mounted on respective shafts so as to be rotated there around. On respective peripheral surface thereof, coating material 2 and 12, which are a non-adhesive material, provided with the elasticity of elastic silicone rubber is respectively disposed. Then, the thickness t1 of the elastic coating material 2 on the first roller 1 is, the same as the thickness t2 of the elastic coating material 12 on the second roller 2. Therefore, by the respective fixing roller 1 and 11 substantially provided with the same structure and substantially arranged with respect to the route 7 of the sheet, the substantially symmetrical operation is performed with respect to both sides 8 and 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a fusing system for use within an electronic copying or printing apparatus that can fuse toner material to both sides of a support material in a single pass. In particular, the present invention relates to a method of fusing an electronic multilayer image onto a sheet by applying heat and pressure.

[0002]

BACKGROUND OF THE INVENTION In electronic printing, and in particular of the first type of electronic printing in electrophotography, the document of the original to be copied or printed is placed on a photosensitive member in the form of a latent electrostatic image. To record. The latent electrostatic image resulting from the deposition of charged particles, commonly referred to as toner, is then made visible to the eye. Preferably, the toner particles have a constant sign of charge and are directly attracted to a pattern of electrostatic charge of the opposite sign in proportion to the strength of the electric field in the individual areas defining the pattern of the image.

[0003] Toner particles that have formed an image visible to the eye are:
It is then transferred from the photosensitive element to a support or image receiving element, such as a flat sheet of paper or a plastics film. Hereinafter, these members are simply referred to as “sheets”. At this time, the toner image is in the form of a loose powder,
It must be permanently fixed or fused onto the sheet with a fusing or fusing device because it is easily disturbed or broken.

In a second type of electronic printing, particularly direct electrostatic printing (DEP), a toner transfer device, such as a magnetic brush assembly, can be processed electronically onto a substrate of an image receiving member called a "sheet". The electrostatic printing is performed directly by the printhead structure. In this case, the toner is deposited directly on the sheet according to the image and no potential electrostatic image is created. The charged toner particles are ejected from a row of holes in the printhead structure by a propulsion electric field applied between the toner transfer device and the support of the image receiving member. The intensity of the toner flow varies according to the pattern of the electrostatic voltage applied to the control electrode. After the deposition step, a fusing step is performed.

A DEP device is disclosed, for example, in US Pat.
935 (Pressman) and European Patent A
No. 0 710 898 (Agfa-Gevaert)
N. V. No.) and need not be further described herein.

The application of thermal energy to permanently fix a toner image to a sheet is well known in the art. By raising the temperature of the toner material to a temperature at which the components of the toner aggregate and become tacky or melt, the toner is absorbed into the fibers of the sheet. That is, they settle on the substrate. Thereafter, as the toner cools, solidification causes the toner to bond firmly to the sheet.

Several methods are known in the art for thermally fusing electronic toner images. Particular attention has now been given to methods of making double-sided copies, ie, front and back copies or prints, ie, copies that produce images on both sides of the sheet.

A problem arises when making double-sided copies, ie front and back copies, because offsets can be severe. This is explained in detail in the next section.

Double-sided printing in an electrophotographic system, such as an electrophotographic copier, which operates in a two-pass (two-pass) manner, can be accomplished in one of the following ways.

(I) The so-called "manual two-pass method". This method requires that a sheet with a multilayer image on both sides, for example a sheet with a colored image, be resupplied by hand. That is, after transferring and fusing the image to the front side of the sheet, the sheet is transported to a take-out tray. The operator then flips the sheet over into the supply tray and passes the sheet through the copier again. This time, the image is transferred and fused to the opposite side of each sheet having the image transferred to the front side.

(Ii) A so-called "method of performing two passes with an automatic delay". In this method, it is necessary to collect sheets of which one side is copied on a tray for double-sided copying. That is, after transferring and fusing the image to the front side of the sheet, the sheet is transported to a tray for duplex copying inside the copying machine.
After the last of a set of sheets has been placed in this duplex tray, all sheets are automatically passed through the copier again. This time, the image is copied and fused on the opposite side of each sheet with the image copied on the front.

(Iii) The so-called “two-pass method that is performed automatically and immediately”. In this method, immediately after the sheets on which the first image has been copied on the front side are fused and stacked together, the sheet on which the image has been transferred to one side needs to be turned over to transfer the image to the other side.

These two-pass copying methods have several disadvantages which are extremely significant, usually associated with two passes through the fuser:

(I) Two passes through the fuser require more energy than a single pass. This is particularly important for multilayer images, for example, colored images. High energy is required to fuse and mix the individual layers or colors.

(Ii) At the same time, the fuser needs to be operated at twice the speed of passing the double-sided sheet.
This is never easily achieved when performing multilayer or collar fusing.

(Iii) The quality of the image is not equal between the front side image and the back side image due to the change in the water content (for example, about 30%) when the first and second copying operations are performed.

(Iv) Furthermore, this change in water content also changes the mechanical properties of the paper, which, combined with the further complexity of the second paper path, results in a second printing operation. Increases the risk of paper jams.

(V) When fusing with a high-temperature roller, a release agent (for example, silicone oil) is required, so that the silicone oil remaining in the first color image stains the image forming element, and again for a long time. Image quality is not kept constant,
There is a possibility that image bleeding or the like may occur.

(Vi) Excessive curling of the paper not only causes trouble in the processing equipment, but also makes handling in the unloading stacker and finishing equipment extremely difficult.

In another system of the prior art, a copying machine for copying both sides in a single pass is described. In the conventional method, three methods are known.

(I) According to the first method, first and second images are sequentially formed on a light receiver. First from receiver
Is transferred to the first side of the image receiving sheet. The sheet is then peeled from the receiver and turned over while the first image is not yet fixed, and a second image is placed on the second side of the image receiving sheet.
Transfer layer. The two images are then fixed on the image receiving sheet in a suitable fuser.

(Ii) Another method of performing two-sided printing in a single pass uses an intermediate image carrier, such as a belt or drum. First and second images are sequentially formed on the light receiver. The first image is transferred to an intermediate image carrier. The light receiving sheet is then passed between the light receiver and the intermediate image carrier. Next, the first and second images are simultaneously transferred to the light receiving sheet.

(Iii) Other systems deal with the "one-pass double-sided copying" method using two light receivers and two exposure systems. A first image is deposited on one light receiver and a second image is deposited on another light receiver. These systems are considered to be the ultimate duplex copy output system. This is because twice as many images can be produced at the same processing speed as in a "two-pass two-sided copying" system.

There are many problems with these traditional one-pass duplex systems.

(I) One problem relates to sending the duplex image receiving sheet to the fuser. In particular, an image receiving sheet with two unfused images on both sides must be sent from the toner transfer station to the fuser. It is preferable not to perform such a transfer using a conventional transfer device. This is because the transfer may cause one of the edges of the image receiving sheet to come into contact and blur the unfused image. It is also preferred that this path be very short in order to prevent the leading edge of the sheet from deviating downwardly from the path between the transfer station and the fusing station. To do so, the fuser must be very close to the receiver. This creates problems with mechanical mounting, problems with the receiver being subjected to undesired heating, and problems with the receiver being contaminated with the fuser release material, such as silicone oil vapors.

(Ii) Further, there is a problem that the speed at which the sheet passes through the fuser of the roller cannot be controlled very much. Clearly, it appears that the transport speed of the light receiving sheet must exactly match the speed of the receiver to prevent "skips" or "bleeds" from occurring during transport. Also, high resolution digital printing cannot tolerate excessive fluctuations in instantaneous photodetector speed ("jitter"). Even in a normal copying machine, it is preferable to separate the fuser roller from the transfer area by a length corresponding to one sheet. For these reasons, it is desirable to thermally isolate and mechanically separate the transfer area of the receiver from the rollers of the hot fuser.

(Iii) In a one-pass two-sided copying system using two or more light receivers and two or more exposure systems,
In general, the copied sheet is wound on a roller after fusing,
Alternatively, a web paper feeder that cuts into sheets is required. Unfortunately, however, this introduces additional mechanical components and complexity into the system. Accordingly, it would be desirable to provide a one-pass duplex copying system with a discontinuous image receiving sheet supply system rather than a web paper supply system.

(Iv) Furthermore, in high quality copying and printing methods, it is ensured that both sides of a sheet that has received an image on both sides experience substantially the same "fusion history", ie, the same temperature and pressure trajectory. You have to do it.

Multilayer electroprinting, for example, multicolor electrophotographic printing, can be considered to be equivalent to a multiple monochrome (commonly referred to as black and white) printing method with various toner layers. However, sequential partial images must be recorded in a superimposed manner. These successive partial images can consist of a superposition of different toner separation images. In one embodiment, for the traditional color components cyan C, magenta M and yellow Y, at least one extra color component is increased according to one toner type. This extra color component can have any other density or tint of cyan, magenta or yellow (obtained by different pigment loadings). In another embodiment, the traditional black component K is added to the three conventional color components. In yet another embodiment, the low pigment loading C'M'Y '(K') for each traditional color component.
At least one second color component CMY or CM
Add YK. According to yet another embodiment, some tonal levels of the original image can be obtained using two different toners having substantially the same chromaticity, or more specifically, two achromatisms. It is reproduced by using a toner, that is, a gray or black toner having substantially zero chromaticity.

In one embodiment, each single toner image is superimposed and transferred onto an image receiving sheet, thereby creating a multilayer toner image on the image receiving sheet. The multilayer toner image is then permanently fixed on an image receiving sheet to produce a multilayer or color copy or print. While fixing a monochrome toner image does not pose a significant problem in practice, fixing a multilayer or color image is much more difficult. In the following description, a discussion will be made on a color image which is a special case of a multilayer image.

(I) Since the color toner image is essentially thicker than the monochrome toner image, for the same print quality and the same print quantity, the supply of heat for fusing is increased, Control must be more strict.

(Ii) As the amount of toner increases, it is necessary to lengthen the fusing time in order to meet the demand for a nip having a large length and a low rotation speed of the fuser roller. The nip between both rollers, or more precisely the nip between the resilient coatings of these rollers, is effectively above the sheet where fusing is initiated by heat and pressure and conveyed between the rollers. It should be noted that this is the area where the fixing of the toner image occurs.

(Iii) The fixing of a multi-layer image requires fixing rollers having very different geometric shapes as compared with the method of fixing a single-layer image by a conventional method. Difficulties are encountered in that a special design must be sought for the geometry, for example the thickness of the resilient coating on each roller, the diameter of the rollers, the pressure applied to the rollers, etc.

A patent of great interest in view of the many problems discussed above is US Pat. No. 4,427,285. However, due to several disadvantages, there are still severe restrictions on the effective use of this patent.

A first limitation to the solution to the problem described in US Pat. No. 4,427,285 is that it is not, or hardly applicable, to fusing multilayer toner images.

A second important limitation of the method described in US Pat. No. 4,427,285 is that this solution requires a device to shut off heat between the fusion station and the receiver.

On the other hand, the patent describes a transfer device for carrying, for example, an image receiving sheet having a toner image transferred to both sides to a heat source for fusing, thereby isolating the light receiver from the heat source.

US Pat. No. 4,427,285 also states that
There are two different functions between the transfer station and the heat supply: (i) to shut off the heat, (i)
i) A heat shielding device which functions to fix an unfused image on an image receiving sheet is described.

As will be apparent from the following detailed description, it is a significant advantage of the present invention that it does not need to be first secured and does not require a densifying roller.

Also, as will be apparent from the following detailed description, no intermediate fusion is necessary. Such an intermediate fusion inevitably increases the manufacturing cost of the apparatus and reduces the dimensional stability of the sheet due to changes in the water content, thus reducing the reliability of the system.

In view of the above, a fusing station of the type described above is mounted on an electronic image producing device designed to perform a single pass fusing in a multi-layer or color duplex printing method of sheet feeding type. Not suitable for

[0042]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and a method for performing high-quality fusing without performing intermediate fusing in a sheet-supply type multilayer duplex copying method.

Other objects of the present invention will become clear from the following description.

[0044]

SUMMARY OF THE INVENTION The object of the present invention is achieved by the features of claim 1.

The characteristics of the preferred embodiment of the invention are set forth in the embodiments of the invention at the end of the specification.

Other advantages and embodiments of the present invention will become apparent from the following description and the accompanying drawings.

[0047]

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described with reference to the accompanying drawings.

The fusing station of the present invention is described and illustrated below with reference to the accompanying drawings, which do not limit the scope of the invention. In the accompanying drawings and the following description, like numerals (for example, 1 and 11) indicate similar members (for example, fixing rollers) having similar operations.

FIG. 1 is a schematic sectional view of a fusion station according to the present invention.

To help better understand the following description and the claims, the meaning of certain terms will first be described.

As used herein, the terms "support material", "image receiving support", "support or substrate member", "image receiving sheet" or simply "sheet" refer to an opaque material that receives the transferred image. Sheets such as paper, white bond paper, resin-coated paper, transparent films, plastics, laminates of both, and adhesive labels. This sheet can be the final product as it is, or it can be an intermediate product in the remanufacturing process. After appropriate treatment, these sheets can be used as so-called transfer elements, for example as printing plates for printing images on the final support by means of lithographic printing. In many experiments performed in the present invention, so-called "1001 paper" sheets having a basis weight of about 100 g / cm < ² > were used.

The word "color" is usually magenta,
Toner with added cyan and yellow and black as needed (CM
However, the present invention is not strictly limited only to the case where a normal color separation image is formed by Y or CMYK.
The term "color" refers to the case where an image is created with more or less than the above three colors; different shades of one color, for example different shades of gray, or multiple layers of one toner. It is also used when producing an image using a transparent, colored, fluorescent or other type of varnish coated according to the image.

The term "printing" firstly describes the output printed image by layering the image with a series of horizontal sweep lines each having a given number of pixels, ie, pixels per inch. Used for the resulting printing press. The exposure station for exposing the record consists of a laser with a rotating mirror block, an array of LEDs, a uniform light source and a number of individually controllable light emitting bulbs, an arrangement with a deformable mirror device (DMD), and the like. However, the term printing also includes devices in which exposure of the recording member is effected by optically projecting an internal image, such as in a copier. Furthermore, the term printing includes DEP devices.

For an overview of electronic copying or printing devices capable of producing color images on both sides of a paper sheet, refer to the pending European Patent Specification A-6 entitled "Electrostatic Color Printing Device".
9.203.561.4 (Agfa-Gevaert)
N. V. Nomenclature). In this specification, an electrostatic color printing apparatus is described which includes an exposing device for sequentially generating partial electrostatic color images on both sides of a recording member in the form of an endless belt. The specification also discloses a developing station for sequentially developing such latent electrostatic images to generate a toner image on the belt, and an image receiving station for sequentially supplying the toner images from the belt through a transfer station. An electrostatic transfer station is described in which a transfer is performed superimposed on a sheet while simultaneously contacting an image receiving sheet with a portion of a belt to create a multicolor duplex image.

FIG. 1 of the present specification shows an embodiment of the fusing device 25 for applying heat and pressure, and its configuration will be described below. The fusing station 25 includes a pair of rollers 1,
11 is included. Each roller comprises a rotating body 3, 13 made of a thermally conductive material, for example a cylindrical aluminum core or tube. Preferably, both thermal conductors have substantially the same diameter and are mounted for rotation about their axis in a manner known in the art. The surrounding surface is provided with a resilient coating 2,12 of a non-adhesive material, for example silicone rubber. The elastic coating material is preferably coated with tetrafluoroethylene, fluorocarbon resin, or the like.

Both rollers 1 and 11 are equipped with internal heating sources 4, 14, for example a tubular infrared lamp.

The fusing device includes a device for pressing the rollers 1 and 11 together. In this way, a nip having an appropriate length is created. In the experiments of the present invention, it was very suitable that the length of the nip was about 9 mm. A sheet having no or only partially fixed image of the deposited thermoplastic powder or toner is passed through this nip to fix the toner to the sheet. The device for pressing the rollers can consist of a spring or a pneumatic mechanism (not shown in FIG. 1).

In the vicinity of the rollers 1 and 11, there are provided devices 5 and 15 for coating the rollers with an anti-set-off solution, release agent or oil. As a result, set-off of the toner is prevented, and the sheet 9 is easily separated from the rollers 1 and 11. Further, a stripping device (not shown) or the like can be attached so that the sheet can be reliably stripped from the rollers 1 and 11.

Now that the description of the basic configuration of the fusing device 25 has been completed, its functional operation will be described. As can be seen from FIG. 1, the sheet 9 having the images 8 and 18 transferred on both sides passes through the fusing station 25. The outer surface of the fuser roller in contact with the sheet 9 of support material is:
It passes through the fusing station 25 at a peripheral speed synchronized with the advance speed of the sheet 9 of support material.

As described above, toner particles are transferred from sheet 9 to roller 1 due to friction or adhesion.
It is important not to set off to 11 or vice versa.

The support material sheet 9 and the rollers 1, 1
In order to prevent friction set-off between the rollers 1 and 11, the rollers 1 and 11 are driven by a suitable motor and a suitable belt or gear (not shown).
Is preferably advanced through the fusing station 25 in synchronization with the advance speed of the sheet 9 of support material. In this way, no set-off of toner occurs between the rollers 1 and 11 and the sheet 9 of the supporting material due to friction.

In order to prevent the toner particles from sticking from the sheet 9 of the support material to the rollers 1 and 11 due to the adhesion of the toner particles to the roller, a peeling agent such as polytetrafluoroethylene or silicone rubber is used. It is known to those skilled in the art to cover the rollers with a surface layer of material or a resilient coating. Since these materials are heat insulating materials, thermal conductivity decreases as the thickness increases,
The thickness of these materials on the rollers must be kept low.

In a fusing station in which a pair of heated rollers 1 and 11 are used and the sheet 9 is passed therethrough, the heated rollers are separated by a releasable material or a resilient coating material 2 or 12. It has been repeated here that it is preferred to coat and to further use release agents 5, 15 such as silicone oil to reduce the problem of settling of the toner material to the heated roller. Please note.

At the fusing station where the paired heating rollers are in contact, the toner material 8, 18 is applied to sheet 9
It is important that the sheet 9 and the pair of heated rollers 1 and 11 are in close contact with each other in order to effectively fuse them together. In fact, all the heat required to fuse the toner material must be transferred to the toner material by heat conduction from a heated roller to the toner material. This means that at the time of fixing, the fused toner is in direct contact with the heated roller and at the same time pressure is applied.

In practice, the temperature of the rollers 1 and 11 is determined by introducing a thermistor, for example, a bimetal inside the roller, or preferably by mounting a temperature detecting element near the surface of the roller, and setting the thermistor to a constant temperature control circuit (Not shown) can be maintained at a predetermined substantially constant value. It is also possible to use more than one temperature sensor, which is preferably located at different positions with respect to the rollers. For example, one temperature sensor is brought into rotational contact with the resilient coatings 2, 12 of the fixing rollers 1, 11 inside the image area, and another temperature sensor is used outside the image area for the same fixing. Contact with the rolls.

For measuring the temperature of the surfaces of the rollers 1 and 11, especially in the image area, a method of sensing the temperature without contact is particularly suitable.

The sheet of the support material 9 is
Upon exiting 5, the sheet is gripped by yet another pair of rollers (not shown) to further transport the sheet toward the copy paper tray and then remove it.

Electrophotographic devices (including electrical photoconductors),
The fusing station 25 of the present invention for use in electrophoretic devices (referred to as toner images created by liquid toner particles), as well as electronic image generating devices such as electrostatographic devices (e.g., DEP devices). A specific example of 1 will be briefly described.

The multi-layer toner image is transferred to a supporting material 9 in sheet form.
At the same time, the sheet 9 is moved along a certain path. The fusing station includes two heated fusing rollers 1 and 11, each of which rotates while in contact with one side of the sheet. A driving device can be used to rotate the fixing roller. The outer surfaces of both rollers move synchronously with the advance speed of the sheet 9. A pressing force is applied to the fixing rollers 1 and 11 by a press device. The heating sources 4 and 14 have substantially the same properties (geometry, spectrum, power, etc.) and are preferably by irradiation. Both fusing rollers have respective resilient coatings 2 and 12, which create a heating nip by the pressure between the two rollers. In this way,
Fusing rollers, preferably of substantially the same construction and arranged substantially symmetrically with respect to the path 7 of the sheet, perform substantially symmetrical operations on both sides 8 and 18 of the sheet. .

In a preferred embodiment of the present invention, the thickness t1 of the resilient coating material 2 of the first roller 1 is
Is equal to the thickness t2 of the elastic covering material 12 of the roller 2. In particular, each fixing roller (about 2.5 m in this example)
m) of the coating material 2, 12 having elasticity (t
The ratio (t1 / t2) of 1 and t2) is 0.9 to 1.1.
, More preferably in the range of 0.95 to 1.05.

In another preferred embodiment of the present invention, the individual fusing rollers (in this example, their diameters D1 and D2
Is about 73.5 mm). The ratio (D1 / D2) of the diameters (D1 and D2) of the outer peripheral portion is in the range of 0.9 to 1.1,
More preferably, it is in the range of 0.95 to 1.05.

In yet another embodiment of the present invention,
Separate power controls allow the outer perimeters of both fusing rollers to be at substantially equal temperatures, eg, about 443K.
(That is, 170 ° C.), each heating source is controlled. In one particularly preferred embodiment, applying a pressing force without heating results in a pressure of about 95%.
At a predetermined speed of mm / sec, it is insufficient to perform fusing without causing set-off of the toner.

The fusing device of the present invention can include a device for treating the surface of the fixing roller so that the fixed sheet can be more easily peeled off. To release the fixed sheet, a release agent such as oil applied to a fixing roller can be used, but a mechanical or pneumatic system can also be used. In this case, the system for fusing the toner image to the sheet includes a heated fusing roller that applies pressure to at least a portion of the toner image on the sheet by a nip created by the pressure between the fusing rollers. . Preferably, the system includes an oil application system for applying oil to the fuser roller.

In particular, in a further preferred embodiment of the present invention, the fusing station further comprises a release applicator or an oil applicator individually arranged on each fusing roller. These oil applicators have a configuration such that the outer periphery of both fusing rollers receives substantially the same layer of release agent, their location relative to the fusing rollers, and individual oil application adjustments.

In another preferred embodiment of the present invention,
The fusing station also includes cleaning devices 6 and 16 located individually on each fuser roller. These cleaning devices have a structure in which the outer peripheral portions of both fixing rollers are cleaned substantially in the same manner, a position with respect to the fixing rollers,
And preferably have individual drive controls.

In yet another preferred embodiment, the heating sources include infrared lamps or halogen quartz lamps each individually mounted inside each fuser roller.

In another embodiment of the invention, a resistance heater can be used to heat the thermally conductive wicks 3,13.

In another preferred embodiment of the fusing station of the present invention, the fuser roller is made from a suitable thermal conductor core 3 and 13 and is capable of deformable materials 2 and 1
An elastic coating is provided by two suitable surface layers. In particular, the outer surface of the fuser roller is covered with a suitable surface layer of a deformable material or a resilient coating, which at least (i) has a soft or elastically deformable thermal conductivity. And (ii) an outer layer of release material.

Preferably, the thermally conductive cores 3 and 13
Is made from copper, aluminum, or alloys of any of these materials. In experiments performed in the present invention, a thickness of, for example, 4.25 mm was suitable.

In another preferred embodiment of the fusing station, the resilient coatings 2 and 12 are silicone rubber or fluoroelastomer. In the experiments carried out in the present invention, silicone rubber having a thickness of, for example, 2.5 mm and a shore hardness of 40 was preferred.

In the fusing station of the present invention, a heat sensor, for example, a thermistor is connected to a constant temperature control circuit,
The temperature of the roller is maintained at a predetermined constant value. This value is set between the temperature at which the resinous toner powder becomes tacky and the fusing temperature of the toner. Preferably, each heating device is adapted to maintain the resilient coating of each roller at substantially the same temperature and to provide a temperature deviation between the rollers within 20K, preferably less than 5K. Power control.

In the fusing station of another preferred embodiment, the resilient coatings 2 and 1 of the fuser roller are used.
The outer surface of 2 is advanced in synchronism with the advancement of the sheet 9 through the fusing station 25 and is in contact with the fuser rollers 1 and 11 such as sensors, cleaning devices, etc.
At least one of the release agent application devices and the like is in contact with rotating in synchronization therewith.

In the fusing station 25 of the present invention,
Most preferably, said path 7 of the sheet is substantially straight, at least between the transfer station and the nip. Preferably, the radius of curvature of the path between the transfer station and the fusing station roller nip is greater than twice the outer diameter of the roller, and more preferably greater than five times.

For good and identical thermal behavior of both fixing rollers, these rollers are made of substantially the same material with respect to the cores 3, 13 and the resilient coatings 2, 12, Further, it is preferable that they have the same thickness and the like. Further, it is preferable that the fixing roller is mounted such that its longitudinal axis is parallel. Generally, both fuser rollers have the same geometric shape, and are often cylindrical. However, cases where the fuser roller has a convex and / or concave geometry (eg, to prevent wrinkling of the sheet) are also within the scope of the present invention.

In addition to the physical fusing station described above, a fusing station 25 such as described above (containing toner images 8 and 18 on both sides of sheet 9) is used to make one-sided or front and back side copies. A method of fixing by a one-pass method is also described.

In another preferred embodiment of the present invention,
The toner images 8 and 18 are multilayer images composed of superimposed color separation images.

In a particular method of the invention, the path 7 of the sheet of support material 9 is substantially horizontal. The word substantially horizontal is defined as [-5 °,
+ 5 °].

In another particular method of the invention, the path 7 of the sheet 9 of support material is substantially vertical. The word substantially vertical is referred to as [-5
°, + 5 °].

Some advantages of the horizontal path are as follows: (i) If the sheets in the feed and unload paper trays are in a horizontal position, this sheet Can follow a linear path, which is very advantageous for making the transport system highly reliable (for example, with very little risk of jamming or wrinkling).

(Ii) The height of the device can be significantly reduced, which would be very easy for the operator.

Some advantages of the vertical path are as follows: (i) Operations on the sheet can be performed with a high degree of symmetry. This is because there is no preferential effect of heat or gravity when viewed from both sides of the sheet.

(Ii) The floor area required for the apparatus can be considerably reduced.

The direction of the path of the seat 9 may be advantageous in other directions and can be tilted within the scope of the invention.

Another preferred method is to use a blank sheet 9, ie, before the sheet receives toner particles, on both sides 8.
And 18, a preheating step acting symmetrically.
By doing this, the mechanical properties of the sheets (e.g., moisture content or difference) can be equalized, the rate of paper jams reduced, and good quality fusing performed.

As is evident from the background of the invention herein, there are several other problems currently to be solved in performing a single-sided, multilayer fusing operation on a sheet in a single pass.

Among these difficulties are the following problems: (i) A sheet having toner adhered to both sides can be removed from a duplex image apparatus without damaging the unfixed image.
The problem of transferring to the double pass fuser in a single pass.

(Ii) Given a particular fusing speed necessary to obtain stable image quality for a wide variety of substrate printing materials, on the other hand, is very limited in the transfer portion of the copier. The problem is that only a small number of separate image generation speeds can be obtained.

(Iii) In addition, the problem is that it is almost impossible to make the fusing and image forming speeds exactly equal, so that the relationship between the two speeds needs to be separated.

In the method of the present invention, these difficulties just mentioned are solved by providing a buffer between the image forming or transfer station and the fusing station. This shock absorber can handle differences in speed, vibration, and the like.

The purpose of the shock absorber will be described in detail below. The fusing station 25 fuses the toner images 8, 18 and transfers them to the sheet 9 for fixing. It should be understood that this operation requires a certain minimum amount of time. This is because the temperature of the fusing device has an upper limit which must not be exceeded. Without this upper limit, roller life would be unsatisfactory. In other words, the speed of the fusing station 25 is limited. On the other hand, the speed of the image generation station (not shown) is not limited in principle for any particular reason. Conversely, it is advantageous to use high speeds for image generation and transfer, since the separation of each color image into its respective (e.g., four) colors is preferably performed sequentially by the exposure station. This means that the recording time of one type of color image is at least four times the recording time of one partial image.
This means that the photoconductor belt, and thus the sheet moving in synchronism therewith, is relatively fast compared to the highest available transport speed through the fusing station. According to some practical test results in the apparatus of the present invention, the speed of the photoconductor belt reached 295 mm / sec, but the fusing speed was 100 mm / sec.

Further, in order to obtain an optimum result, it is desirable to adjust the fusing speed independently of the image processing speed. It should be noted that the image processing speed at the image station is preferably constant.

The length of the buffer station must be long enough to receive the largest sheet to be processed by the device.

Since the buffer station is initially operated at the speed of the photoconductor belt, the speed of this buffer station is reduced to the processing speed of the fusing station 25 as the trailing edge of the sheet exits the imaging station. .

European Patent Specification 96.200.97
As described in 7.5 (in the name of Agfa-Gevaert NV), for a single color, an almost single layer of toner particles is deposited thinly to completely eliminate It is preferred to adjust the amount and / or degree of dispersion of the pigment in the toner particles so that a saturated density is achieved. By doing this, differences in gloss due to differences (possibly large differences) in the thickness of the various layers of deposited toner particles are minimized.

In one preferred embodiment, the mass of toner particles deposited per unit area (toner mass (T.sub.T) to obtain the highest optical density for each single color.
M)) follows the formula: TM ≦ 0.8 × _dv50 × ρ [1] where TM is expressed in mg / cm ² and dv50 is c
m is the average volume diameter of the toner particles, where ρ is g /
is the bulk density of the toner particles in cm ³ (eg, ρ =
1.1~1.3g / cm ^3).

As used herein, the term maximum optical density for each single color refers to 1.4-1.6 for yellow, magenta and cyan, and 1.6-1.6 for black. Means the optical density on the reflective support in the range of 2.0.

Therefore, a complete color image, for example, composed of four color toners YMCK, and each toner has d _v50 = 8 ×
To produce an image of 10 ⁻⁴ cm and a density of 1.25 g / cm ³ , the very darkly colored areas were each made with about 0.8 mg / cm ² of toner at about 2.
It is formed by superimposing five layers. About 2.5mg obtained
/ Cm ² toner layer is very difficult to fix and requires special methods.

The apparatus and method for fixing a multilayer toner image to a sheet of support material in a single pass are as described immediately above. Also described is a method particularly suitable for fixing double-sided copies.

In another embodiment of the present invention, the highest optical density for black (ie, 1.6 to 2.0 on a reflective support).
The amount TM of the toner particles deposited to obtain an optical density of 0) follows the formula: TM ≦ 0.8 × _dv50 × ρ [1] where TM is expressed in mg / cm ^{2 and} _dv50 Is the average volume diameter of the toner particles in cm, and ρ is g / cm
It is the bulk density of ³ units of toner particles.

In another preferred embodiment of the present invention, the highest optical densities for each of the single colors yellow, magenta, and cyan (ie, 1.4-1.4 on a reflective support).
The amount TM of the toner to be deposited to obtain 1.6) follows the same equation: TM ≦ 0.8 × _dv50 × ρ [1]. Where TM is expressed in mg / cm ² and d _v50
Is the average volume diameter of the toner particles in cm, and ρ is the bulk density of the toner particles in g / cm ³ .

For example, European Patent A-0 656 1
No. 29, A-0 629 921, A-048
No. 6,235, U.S. Pat. Nos. 5,234,783 and 4,
No. 828 950, European Patent A-0 554 9
No. 81, WO 93/07541 and Xer
ox Research Disclosure Jo
urnal, Vol. 16, No. 1, p. 69 (1991, January 1)
When an image is developed with a colorless toner as exemplified in the month / February issue, it is preferable that the colorless toner be deposited in an amount TM satisfying the formula [1].

In this case, the present invention can be applied.

APPLICATION The method of fixing by applying heat and pressure by contact according to the present invention is advantageous in that it requires less electric power and has much less risk of fire and sheet burning than fixing using radiant heat. There.

Even if some characteristics of the system are different, for example, the difference in the roughness of the back side with respect to the front side of the sheet,
It is a remarkable feature of the present invention that the quality of the images on both sides can be equalized even if there are differences in the structure or position of the release agent applicator, differences in the thermal effects of both fixing rollers, and the like.

For the purposes of the present invention, an electrostatic latent image can be created by exposing an electrostatically charged photoconductor member to an optical image of a document to be an original. Alternatively, an electrostatic latent image can be created by exposing the photoconductor member to a number of separate spot-shaped radiation sources that are appropriately activated. This separate spot radiation source can be created by a linearly arranged light emitting diode (LES) or laser, which can modulate its beam to receive or receive radiation during each scanning motion. Determine the location of a number of independent pixels.

Obviously, a method in which the fusing station 5 of the present invention is used to perform fixing in a single pass of single-sided copying (the toner image is present on one side of the sheet) is also included in the scope of the present invention.

The present invention can also be used in a method for obtaining double-sided single-sided copying or printing in a single pass to a double-sided copying machine or printing machine.

The method uses (i) two image receiving sheets for one copy or print cycle, which are placed along a common path through the printing press in a back-to-back relationship. (Ii) forming one toner image on one side of one image receiving sheet and another toner image on the other side of the other sheet while passing both image receiving sheets through the printing press simultaneously, (Iii) fixing toner images on both sheets. For further information see European Patent Specification A-96.02035.58.0 (in the name of Agfa-Gevaert NV).

In one preferred embodiment, it is desirable to provide a single pass, duplex system having separate image receiving sheet supply systems. With the concept of a symmetric fusing operation as in the present invention, a web paper supply system can be used at any time.

Apart from traditional toner images made from dried toner particles, the present invention can also be practiced with liquid toner particles, such as toner images made by electrophoresis.

Further, as described at the beginning of this specification, the fusing apparatus of the present invention is used for fusing an electronic multilayer image, for example, an electrophotographic color image, for either one-sided or two-sided copying. It would be particularly interesting to use

However, there is still more interest in using the present invention for fusing double-sided color images. This is because the problem of the fluctuation of the surface temperature of the fixing roller becomes more severe for such an application. In this regard, reference is made to the above-pending European Patent Application A-96.203.561.4.

As will be apparent to those skilled in the art, other types of fusion stations, such as short wavelength lamps (eg, infrared lamps), medium or long wavelength radiators (eg, resistor or ceramic elements) Or flash
Also for fusing stations using direct radiators such as lamps (thus not incorporated in the rollers), fusing stations using electromagnetic waves (eg microwaves), fusing stations using hot air, etc. Advantageously, such a buffer may be used between the imaging station and the fusing station.

In another embodiment of the present invention, a symmetric fusing operation can be achieved using a fusing station using hot air. In this case, the fusing takes place almost non-contacting (meaning that virtually no rollers or plates are in contact with the sheet during fusing) and the hot air is controlled symmetrically on both sides of the sheet with control. . From time to time, the flow rate and temperature of the hot air must be adjusted within an acceptable range.

[0125] Such fusing methods include the step of moving the sheet, which can be performed by various mechanisms. Gravity, belts, such as moving a sheet along a downward vertical path
Clamping mechanisms or other transport devices that grip at the non-image edge include devices that maintain the sheet fusing direction, devices that maintain contact with the sheet edge, and the like.

Such a fusing method involves simultaneously heating the sheet while moving the sheet by symmetrically supplying hot air in a manner that can be implemented by various mechanisms. This can be done, for example, by a set of two perforated plates arranged on both sides of the sheet on the path through which the sheet passes. (See, for example, FIG. 2).

Such hot air fulfills two different functions: (i) an air cushion function which assists the non-contact movement of the seat.

(Ii) A fusing function by symmetrically and uniformly heating both sides of the sheet.

In summary, another preferred embodiment of a method for fusing a double pass or front and back copy of a color image with a resinous powder to a support material in a single pass is to use (i) a fusing station. Moving the sheet through a predetermined path through, and (ii) simultaneously supplying hot air to both sides of the sheet at the fusing station, wherein the fusing station has substantially the same operation. A source of air having characteristics, wherein the supply of air comprises heating the hot air to a substantially equal temperature and applying the hot air to both sides of the sheet at substantially equal flow rates to the sheet. It is characterized in that a symmetric fixing operation on both sides is obtained. It should be added that this embodiment is also applicable to web-shaped image receiving support materials, rather than to separate sheets in a strict sense.

It will be apparent to those skilled in the art that various modifications can be made based on the above description without departing from the scope of the present invention.

Among these variations, before transferring the toner image, the sheet supplied from the supply stack (not shown in FIG. 1) is subjected to a drying operation as needed, and a sufficiently low water content of, for example, 60% or less is applied. It can have a content.

Another variant provided by the present invention involves a preheating step performed on a blank sheet prior to the fusing step, or even before the transfer or development step. Such preheating increases the construction cost of the equipment but reduces the operation cost of the equipment.The effect of reducing the fixing energy in the fixing process reduces the change in sheet moisture and the rate of paper jams. Is obtained.

The main features and embodiments of the present invention are as follows.

1. It includes a pair of pressure rollers having a nip, each roller (1, 11) simultaneously contacting one side of the support material, and each roller having a toner image (at its nip) on one side of the support material ( (8, 18), and a heating device (4, 14) for heating the resilient coating of the rollers (4, 14). In a fusing station (25) for fixing 8, 18) onto a sheet of support material (9), the rollers have substantially equal outer diameters (D1, D2) and the first roller (1) Material with elasticity (2)
A welding station wherein the thickness (t1) of the second roller (2) is substantially equal to the thickness (t2) of the resilient coating (12).

2.2 Outer diameters (D1, D1) of each of the two rollers
The ratio of 2) is 0.9 to 1.1, preferably 0.95 to 1.
The fusing station of claim 1 wherein the fusing station is in the range of 05.

[0136] 3. The elastic covering material (2, 12)
2. The fusing station according to claim 1, wherein the has a thickness of more than 1.5 mm, preferably more than 2.5 mm.

4. 4. The fusing station according to claim 1, wherein the length of the nip is greater than 3 mm, preferably greater than 5 mm, more preferably greater than 7 mm.

[0138] 5. A separate power control device for each heating device to maintain the resilient coating of each roller at a substantially equal temperature, such that the temperature deviation between the rollers is less than 20K, preferably less than 5K. The fusing station according to claim 1, further comprising:

6. Each of the rollers is provided with a release agent applicator (5,
A fusing station according to any of claims 1 to 5, which is connected to (15).

7. Each of the rollers is provided with a cleaning device (6, 1).
7. The fusing station according to claim 1, which is connected to (6).

8. 8. The fusing station according to claim 1, wherein the resilient coating of each roller is arranged to advance at a peripheral speed synchronized with the sheet passing through the fusing station.

9. At least one device in contact with the rollers has a peripheral speed synchronized with the sheet passing through the fusing station, and the speed deviation between each other is preferably less than 10%, more preferably less than 2%. 8. The fusion station according to 8.

10. An apparatus for moving a sheet of support material through a predetermined path through a fusing station and fusing to fix a multi-layered toner image on the sheet of support material having a device for supplying hot air to both sides of the sheet. At the station, the hot air is heated by a heating source having substantially the same operating characteristics, the hot air is applied on both sides of the sheet at substantially equal flow rates, and the flows of hot air are substantially equal A fusion station that is heated to a temperature.

11. The fusing station according to any of the preceding claims, wherein the multi-layer toner image (8, 18) comprises dry toner particles.

12. The fusing station of claim 1, wherein the fusing station is arranged to move the sheet along a path between a toner transfer station and an entrance of the fusing station, the path being substantially straight.

13. A method for fusing a duplex copy having a toner image on both sides of a sheet using the fusing station of claim 1.

14. (I) moving the sheet of support material through a predetermined path through the fusing station;
(Ii) A method for fixing a duplex copy of a toner image to a sheet of support material comprising the step of supplying hot air to both sides of the sheet, wherein the hot air is heated by a heating source having substantially the same operating characteristics. Wherein the hot air is applied to both sides of the sheet at substantially equal flow rates and the flow of hot air is heated to substantially equal temperatures.

15. 15. The method according to claim 13, wherein the toner image is a multicolor image in which separated color images are superimposed.

16. 14. The method according to claim 13, further comprising the step of performing preheating, preferably preheating that acts symmetrically on both sides of the sheet.
The method of any one of claims 15 to 15.

17. A method for fixing a one-sided copy having a toner image on one side of a sheet in one pass using the fusing station according to claim 1.

18. 13. A method for fixing a double-sided copy in an electrophotographic apparatus using the fusing station according to claim 1, wherein (i) two image-receiving sheets are used for one printing cycle, (Ii) create one toner image on one side of the image receiving sheet and another toner image on the other side of the other sheet while both sheets are Producing a two-sided print by simultaneous movement through said apparatus, and (iii) fixing the toner images to both sheets.

19. The amount TM of the toner particles deposited to obtain the maximum optical density for black is represented by the formula TM ≦ 0.8 × _dv50 × ρ [1] where TM is expressed in mg / cm ² , and _dv50 is cm
Is the average volume diameter of the toner particles in units, and ρ is the bulk density of the toner particles in g / cm ³ ,
The amount of toner particles TM deposited to obtain the maximum optical density for each of the single colors of yellow, magenta and cyan
Is the formula TM ≦ 0.8 × _dv50 × ρ [1] where TM is expressed in mg / cm ² , and _dv50 is cm
Is the average volume diameter of the toner particles in units, and ρ is the bulk density of the toner particles in g / cm ³ ,
The method according to claims 15 to 18 according to claim 15.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fusing station of the present invention including a pair of pressure rollers.

FIG. 2 is a schematic diagram of another fusing station of the present invention that includes a hot air flow.

[Description of Signs] 1, 11 Roller 2, 12 Elastic coating material 3, 13 Thermal conductive core 4, 14 Heat source 5, 15 Release agent applicator (oil applicator) 6, 16 Cleaning device 7 , 17 Path 8, 18 Toner Material 9 Sheet 25 Fusing Station

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Sergiu Tavernier Belgium B 2640 Malt Cell Septes Trat 27 Agfa-Gevuert na Mrose Fennoutjaps (72) Inventor Liyuk van Aken Belgium B 2640 Maltcell Septes Trat 27 in Agfa-Gevert Na Mrose Fennoutjap (72) Inventor Liyuk van Getem Belgium 2640 Maltcell Septes Trat 27 Agfa-Gevert Gernfeld Jennoutjjap Inside

Claims (6)

[Claims] 1. A method comprising: a pair of pressure rollers having a nip;
Each roller simultaneously contacts one side of the support material, each roller having a resilient coating that contacts the toner image on one side of the support material at its nip, and an elasticity of the roller. A fusing station for fixing the multi-layer toner image onto a sheet of support material, the roller having substantially equal outer diameters, the first roller comprising: A fusing station, wherein the thickness of the resilient coating of the second roller is substantially equal to the thickness of the resilient coating of the second roller. 2. Multi-layer toner on a sheet of support material having a device for moving a sheet of support material through a predetermined path through a fusing station, and a device for supplying hot air to both sides of the sheet. In a fixing station for fixing an image, the hot air is heated by a heating source having substantially the same operating characteristics, the hot air is applied at substantially equal flow rates on both sides of the sheet, and the flow of hot air is A fusing station characterized by being heated to substantially equal temperatures. 3. A method for fixing a duplex copy having a toner image on both sides of a sheet, using the fusing station according to claim 1. 4. A method comprising: (i) moving a sheet of support material through a predetermined path through a fusing station; and (ii) supplying hot air to both sides of the sheet. In a method of fusing duplex copies of an image, the hot air is heated by a heating source having substantially the same operating characteristics, the hot air is applied to both sides of the sheet at substantially equal flow rates, A method wherein the streams are heated to substantially equal temperatures. 5. A method for fusing a single-sided copy having a toner image on one side of a sheet in one pass using the fusing station of claim 1 or 2. 6. A method for fixing a double-sided copy in an electrophotographic apparatus using the fusing station according to claim 1 or 2, wherein (i) using two image receiving sheets for one printing cycle. Transporting it back and forth along a common path through the device, (ii) creating one toner image on one side of the receiving sheet and another toner image on the other side of the other sheet; Moving both sheets simultaneously through the apparatus to produce two duplex prints, and (iii) fixing the toner images to both sheets.